Cold engine making BAD grinding noise from 2500-300 rpms

[SLC98M3]

My 91' 535i engine has been making a grinding or vibration noise between 2500-3000 rpms. Once the rpms are above 3000 the noise goes away and the engine sounds and runs fine. Temps have been cold with daily highs around 17-25 degrees. Vibration is really bad until the engine warms It sounds as if it coming from the bottom of the engine block. Vibration is less once engine warms up, but is still there. Any thoughts? Thanks in advance. Maybe I just need to move to SoCal.

[strad]

hmm. I'd take the belts off and check each accessory individually to see if the bearings are going out (alt, ac compressor, wp, ps pump). It's also possible your oil pump is loose/not making proper pressure, but I'd suspect an accessory first.